Pallidal and entopeduncular single unit activity in cats during drinking.

It has been shown that pallidal units display changes in firing rate during food seeking and consummatory behavior. The purpose of the present work was to determine which properties of the ingested material or ingestive behavior were most potent in altering unit activity. Single unit activity was recorded in the globus pallidus and entopeduncular nucleus of awake restrained cats during introduction of fluid into the mouth. A very high proportion of pallidal and entopeduncular neurons showed changes in firing rate during fluid injection. Two patterns of response were observed. Typically, responses were phasic and time-locked to the occurrence of fluid presentation. Less frequently, a long lasting change in firing occurred which persisted throughout the period of fluid introduction. Additional observations indicated that both of these changes in firing rate seemed to be related to the sensory rather than the motor aspects of ingestion.